Radio circuit



a B. WATTS JR 2,340,352

RADIO CIRCUIT Filed May 18, 1942 2 Sheets-Sheet l 'INVENTGR 015.952 8. 144417.; Je.

ATTORNEY 1944- c. B. WATTS, JR

RADIO CIRCUIT Filed May 18, 1942 2 Sheets-Sheet 2 WIN-PUT sank/s2 v ewe/gear Q Q mv m- CHESTER 5; WATTS ale BY x ATTORNEY Patented Feb. 1, 1944 PATENT OFFICE RADIO CIRCUIT Chester B. Watts, In, East Grange, N. J.', assignor to Federal Telephone and Radio Corporation,

a corporation of Delaware Application May 18, 1942, Serial No; 443,391 12 Claims. (Cl. 179171.5)

This invention relates to radio-frequency circuits and;more particularly to amplifier, modulator and other circuit parts thereof having multiple vacuum tube arrangements for operation at ultra-high frequencies.

1 .When ultra-high frequency currents are used on the existing amplifier, modulator and other circuits of the prior art having multiple tube'arrangements, the operating results are not satis-' factory One of the difficulties found in using the existing multiple vacuum tube circuits of the prior art at ultra-high frequencies is that the capacitative reactance of such circuits with respect to the higher frequencies is so low that it is impossible for'practical purposes to properly tune the common tank circuits. This unusually large capacitance, I discover, is largely due to the parallel arrangement of, tie-lines and other connections between the/terminals of the tubes. In order to avoid the-occurrence of such large capacitance in multiple vacuum tube operation at ultra-high frequencies, and to otherwise improve the operation of amplifier and other radiocircuit parts having amplifying characteristics, I

arrange each tube or pair of tubes as a separate amplifier having its own grid tank, plate tank and preferably with at least partially separate biasing means, by-pass condensers, and connect together these amplifiers throughlengths of tie- 'lines 'equal electrically to substantially one-half of the wave length of the ultra-high frequency impressed thereon. This circuit arrangement, I

find, greatly minimizes the heretofore capacitance found to occur in the existing multiple tube circuitsof the prior art when operated at ultra-high frequencies.

One of the objects ofthis invention, therefore, is to provide a low capacitance circuit having a multiple vacuum tube arrangement suitable for operation at ultra-high frequencies.

Another object of the invention is to provide a low capacitance circuit having two or more Fig. 2 is a schematic illustration of another amplifier circuit having an input for a source of modulating frequency current by which an input ultra-high frequency carrier current can be amplified and modulated.

Referring to Fig.1 of the drawings, the circuit shown for purposes of illustration contains three sets of vacuum tubes l0, H; l2, l3; and M, II; the circuit of eachs'et bein'gconnected as an individual push-pull amplifier. These amplifier units are connected together in parallel as hereinafter described so that the output power of a plurality of such units is equal to that of one \init multiplied by the number -of units so conls'nect-ed, it beingunderstood, of course, that any desired number of amplifier units may be connected together in' accordance with this invention. 5

Referring particularly/to the amplifier circuit for the tubes l0 and l l, the grids and II thereof are connected together by a suitable tank circuit 24 having a variable condenser 25. The

/ I plates 26 and 2'! are likewise connected together by a tank circuit 28 having a variable condenser gether by a wire 32, and a battery 34 isconnected between the wire 32 and the tank circuit to provide a suitable potential for the grids 2!! and 2|. Asuitable potential for the plates 28 and 21 is provided by connecting the tank circuit 28 at its midpoint by a wire 38 to thewire 42 through a battery 39. The tubes may in addition be provided, if desired, with a screen grid suitably connected in the circuit. 7

The circuits of thetubes l0 and II are thus arranged in push-pull relationship, the two tubes being videntical'and operated at the same continuous grid and plate potentials, and excited in phase opposition by an electromotive force to be amplified. The two sets of tubes l2, l3 and l4, l5 are provided with push-pull circuit arrangements similar to the arrangement described for the set of tubes l0 and II.

The grid terminals of the tubes l0 and II to which the tank circuit thereof is connected are connected in parallel by tie-lines 44 and 45 with the terminals of the. grids of the tubes l2 and i3, and the latter terminals are connected in par-' allel by tie-lines 4B and 41 to the terminals of the tubes I4 and I5. Likewise,..the terminals of the plates 26 and 21 are connected by tie-lines and 52 in parallel to'the terminals of the plates of the tubes l2 and I3 and the plates of the tubes I2 and I3 are connected by tie-lines 54 and 55 in parallel to the plates of tubes I4 and I5. Each of these tie-lines is of a length 29. The filaments and 3! areconnected toequal electrically to substantially one-half of the wave length of the high frequency current to be amplified. These parallel tie-line connections being chosen at substantially one half wave length greatly minimize the capacitance effect otherwise present in the prior existing circuits when operated at ultra-high frequencies. It will be understood, however, that while the circuits of my invention are particularly adapted for use at ultra-high frequencies, they may also be used satisfactorily at lower frequencies.

The electromotive force input to be amplified may be applied to any one of the grid. tank circuits of the three sets of tubes. As shown in Fig. 1, the input circuit 60 is shown coupled with the grid tank circuit 24 of the tubes I and II.

While the output circuit may likewise be coupled with any of the plate tank circuits of the three sets of tubes, I prefer as shown to couple the out' put circuit 62 with the tank circuit 63 of the tubes I4 and I5 diagonally disposed with respect to the input circuit 80.

In use, each set of tubes operates as an individual push-pull amplifier and the parallel tie-line connections of the grid and plate tank circuits give parallel inputs and additive power output. The input alternating electromotive force is impressed over the parallel connections to each of the grid tank circuits and excite the grids of the two tubes of each set in phase opposition. That is to say, the grid 20 of tube I0 is positive or less negative when the grid 2| of tube II is at a maximum negative potential and vice versa. This results in the well-known pushpull amplification of the input electromotive force, and the units being connected in parallel, the power output is additive, the summation thereof being transmitted to the output circuit Modulated electromotive force of ultra-big frequencies may be effected by two push-pull units of my invention. Such a modulating circuit is shown in Fig. 2. The two push-pull units including the tubes 10, H and", 13 respectively may be arranged in substantially the same circuit arrangements shown in Fig. 1. The tubes and 'H are provided with a grid tank circuit 14 and a plate tank circuit 15. The tubes 12 and 13 are provided with a grid tank circuit 16 and a plate tank circuit 11. The potential of the grid tank circuits II and may, for sake of simplicity, be provided by connecting indidividual batteries 80 and 80a between the respective tanks and ground. The potential of the plate tanks may be provided by connecting the tanks to opposite ends of a secondary winding I02 of a transformer I00 used as an input for a source of modulation frequency, the center tap of which is connected through a battery I04 to ground I05. i

The two push-pull circuits are connected together in parallel by tie-lines equal electrically in length to substantially one half of the wave length of the input carrier frequency. iIwo of the tie-lines 90 and 9| connect the terminals of the grid tanks of the two push-pull units and tie-lines 92 and 93 connect the terminals of the plate tanks of the two units.

In order to make the output of the two. .pushpull units-in phase opposition, either the tielines90, BI or the tie-lines 92, 93, may be transposed. As shown in Fig. 2, the tie-lines 90 and SI are transposed at 95 so that the grid of tube 10'is connected to the grid of tube 13, and the grid of tube II is connected to the grid of tube 12. By this arrangement, the carrier frequency applied to the grid tank circuits by the inputcircuit 94 operates the two units in phase opposition so that the plate electromotive force of the tank circuits l5 and 11 buck each other and therefore tend to balance.

While the transformer. I00 is shown to be connected across the plate tank circuits l5 and I1, it will be readily apparent to those skilled in the art that the transformer may be connected across the grid tank circuit 74 and 16 and the batteries and 80a transposed to provide potential for the plate tank circuits l5 and 1 1.

An output circuit IIO ,may be coupled with either of the plate tank circuits [5 or I1. As shown, the output circuit is coupled with the plate circuit 11 diagonally opposite the input circuit 94.

In operation, the input carrier frequency which, in accordance with my invention, may be ultra-high, is applied to the grid tank circuits of the push-pull units through-the input circuit 94. The grid tanks of the two push-pull units having the tie-lines therebetween trans-' posed operate in phase opposition so that the plate frequencies of the two circuits are directly opposed and therefore tend to balance each other. The input of a modulating frequency is provided by connecting the transformer primary I06 to a suitable source of modulating frequency. This modulating input unbalances the current conditions of the plate circuits thereby resulting in a carrier output current of ultrahigh frequency modulated in accordance with the input modulation frequency. The modulation is of the carrier-suppressed type giving only side bands.

The parallel connecting tie-lines 90, 9|, 92 and 93 being one-half of the wave length of the carrier frequency, the heretofore high capacitance effect of the connections are avoided and ultra.v high frequencies are effectively amplilied and modulated.

From the foregoing description, it will be readily apparent that the amplifying characteristics of the push-pull units of a circuit, such as illustrated in either of the embodiments (Fig. 1 or Fig. 2), are substantially the same; that the input power can be fed to any one of the grid tanks thereof and that the output power can be taken from any one of the plate tanks thereof; that the grid tank circuits of each embodiment act together as one and the plate tank circuits of each embodiment act together as one; and that the tuning of any grid tank operates to influence the tuning of the other grid tanks connected thereto and the tuning of any plate tank circuit operates to influence the tuning of the other plate tanks connected thereto. Each separate tank circuit should preferably be tuned correctly in order to have good powerdistribution. This may be done by tuning all the grid tanks with the same condenser settings and all the plate tanks with the same condenser settings.

It is recognized that many variations and changes may be made in the circuits shown and described without departing from the invention. It will be understood, therefore, that the circuits shown and described are to be regarded as illustrative of the invention only and not as restricting the appended claims.

What I claim is: i

- 1. In a radio frequency circuit, a part thereof comprising a plurality of pairs 01 three-electrode vacuum tubes, a grid tank circuit for each pair con'- necting together the terminals of the grid tank circuits, and other tie-lines connecting together the terminals of the plate tank circuits.

2, In a radio frequency circuit, a part thereof comprising a plurality of pairs of three-electrode vacuum tubes. a grid tank circuit for each pair of tubes connecting together the grids thereof, a plate tank circuit for each pair of tubes connecting together the plates thereofitie-lines connect ing together the terminals of the grid tank circuits, other tie-lines connecting together the terminals of the plate tank circuits, and the lengths of the tie-lines each being equal electrically to substantially one half of the wave length of the frequency input thereto.

3. In a radio frequency circuit, a part thereof comprising a plurality of pairs of three-electrode vacuum tubes, a grid tank circuit for each pair of tubes connecting together the grids thereof, a. plate tank circuit for each pair of tubes connecting together the plates thereof, tie-lines connecting together the terminals of the grid tank circuits, other tie-lines connecting together the terminals of the plate tank circuits, an input circuit electrically coupled to one of said grid tank circuits, and an output circuit electrically coupled to one of said tank plate circuits.

4. In a radio frequency circuit, a part thereof comprising a plurality of pairs of three-electrode vacuum tubes, a grid tank circuit for each pair of tubes connecting together the grids thereof, a plate tank circuit for each pair of tubes connecting together the plates thereof, tie-lines connecting together the terminals of the grid tank circuits, other tie-lines connecting together the terminals of the plate tank circuits, the grid tank circuit of the first of the pairs of tubes being electrically coupled to an input circuit carrying an electromotive force of a given frequency, and the tank plate circuit of the last ofthe pairs of tubes being electrically coupled to an output circuit.

5. An amplifier circuit for an electromotive force of high frequency comprising a plurality of pairs of three-electrode vacuum tubes, 1!. grid tank circuit for each pair of tubes connecting together the grids thereof, a plate tank circuit for each pair of tubes connecting together the plates thereof, tie-lines connecting in parallel the corresponding terminals of the grid tank circuits, tie-lines connecting in parallel the corresponding terminals of the plate tank circuits, the grid tank circuit of the first of the pairs of tubes being electrically coupled to an input circuit, the tank plate circuit of the last of the pairs of tubes being electrically coupled to an output circuit and the lengths of the tie-lines each being equal electrically to substantially one half of the wave length of the input frequency.

6. A circuit for amplifying an electromotive force of high frequency comprising a plurality of push-pull amplifier units, tie-lines connecting in parallel the corresponding grid terminals of the tubes of successive units, tie-lines connecting in parallel the corresponding plate terminals of the tubes of successive units, and the lengths of the tie-lines'each being equal electrically to substantially one-half of the wavelengthof the input frequency.

7. A circuit for amplifying an electromotive force of high frequency and modulating the same comprising a plurality of push-pull amplifier units, tie-lines connecting the grid terminals of the tubes of successive units, tie-lines connecting the plate terminals of the tubes of successive units, the tie-linesbeing so connected that the plate currents tend to balance, the lengths of the tie-lines each being equal electrically to substantially one-half of the wavelength of the input frequency, and means to impose on the circuit a source of modulating frequency.

8. A circuit for amplifying an electromotive force of high frequency and modulating the same comprising a plurality of pairs of three-electrode tubes, a grid tank circuit for each pair of tubes connecting together the grids thereof, a plate tank circuit for each pair of tubes connecting together the plates thereof, a pair of tie-lines connecting the terminals of the grid tank circuits, a pair of tie-lines connecting, the terminals of the plate tank circuits, one of the pairs of tie-lines being transposed so that the electromotive forces of the plate circuits of the pairs of tubes tend to balance, and means to impose on one of the tank circuits of each pair of tubes a source of modulating frequency.

9. A circuit for amplifying an electromotive force of high frequency and modulating the same comprising a plurality of pairs of three-electrode tubes, a grid tank circuit for each pair of tubes connecting together the grids thereof, a plate tank circuit for each pair of tubes connecting together the plates thereof, a pair of tie-lines connecting the terminals of the grid tank circuit, a pair of tie-lines connecting the terminals of theplate tank circuits, the tie-lines each being equal electrically to substantially one-half of the wavelength of the high frequency applied thereto, one of the pairs of tie-lines being transposed so that the plate currents of the pairs of tubes tend to balance, and means to impose on one of the tank circuits of each pair of tubes a source of modulating frequency. v

10. A circuit for amplifying an electromotive force of high frequency and modulating the same comprising two pairs of three-electrode tubes, a grid tank circuit for each pair of tubes connecting together the grids thereof, a plate tank circuit for each pair of tubes connecting together the plates thereof, a pair of tie-lines connecting the terminals of the grid tank circuit, a pair of tielines connecting the terminals of the plate tank circuits, one of the pairs of tie-lines being transposed so that the plate currentsof the two sets of tubes tend to balance, a source of potential connected between the grid tanks of each set of tubes and the ground, an input transformer connectable to a source of modulating frequency, the secondary winding of which is connected between the plate tank circuits of the two sets of tubes. and a source of potential connected between the mid-point of said secondary winding and the ground.

11. A circuit for amplifying an electromotive force of high frequency and modulating the same comprising two pairs of three-electrode tubes, a grid tank circuit for each pair of tubes connecting together the grids thereof, a plate tank circuit a source or potential connected between the grid tanks of each set of tubes and the around, an im put transformer connectable to a source of modulating frequency, the secondary winding of which is connected between the plate tank circuits of the two sets of tubes, and a source of potential connected between the mid-point of said secondary Winding and the ground.

12. A circuit for amplifying an electromotive force of high frequency and modulating the same comprising two pairs of three-electrode tubes, a grid tank circuit for each pair oi. tubes connecting together the grids thereof, a plate tank circuit for each pair of tubes connecting'together the-- plates thereof, a pair of tie-lines connecting the 

